<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="../vue.js"></script>
  </head>

  <body>
    <div id="app">
      <h1>{{isHot?"热啊":"冻啊"}}</h1>
      {{count}}
      <button @click="isHot = !isHot">change</button>
    </div>
    <script>
      Vue.config.productionTip = false;

      const vm = new Vue({
        el: "#app",
        data() {
          return {
            isHot: true,
            count: 0,
          };
        },
      });

      /* 
        在vue实例vm上有一个$watch方法 也可以处理对vm实例上的属性进行监听
        参数1:被监听的属性
        参数2:回调函数
        参数3:配置对象  deep immediate
      */
      vm.$watch(
        "isHot",
        () => {
          console.log("监听有更新了");
        },
        {
          immediate: true,
        }
      );

      vm.$watch(
        "count",
        () => {
          console.log("监听有更新了1");
        },
        {
          immediate: true,
        }
      );
    </script>
  </body>
</html>
